Keratin-binding ability of the N-terminal Solo domain of Solo is critical for its function in cellular mechanotransduction

Sachiko Fujiwara, Tsubasa S. Matsui, Kazumasa Ohashi, Kensaku Mizuno, Shinji Deguchi

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Solo (ARHGEF40) is a RhoA-targeting guanine nucleotide exchange factor that regulates tensional force-induced cytoskeletal reorganization. Solo binds to keratin 8/keratin 18 (K8/K18) filaments through multiple sites, but the roles of these interactions in the localization and mechanotransduction-regulating function of Solo remain unclear. Here, we constructed two Solo mutants (L14R/L17R and L49R/L52R) with leucine-to-arginine replacements in the N-terminal conserved region (which we termed the Solo domain) and analyzed their K18-binding activities. These mutations markedly decreased the K18-binding ability of the N-terminal fragment (residues 1–329) of Solo but had no apparent effect on the K18-binding ability of full-length (FL) Solo. When expressed in cultured cells, wild-type Solo-FL showed a unique punctate localization near the ventral surface of cells and caused the reinforcement of actin filaments. In contrast, despite retaining the K18-binding ability, the L14R/L17R and L49R/L52R mutants of Solo-FL were diffusely distributed in the cytoplasm and barely induced actin cytoskeletal reinforcement. Furthermore, wild-type Solo-FL promoted traction force generation against extracellular matrices and tensional force-induced stress fiber reinforcement, but its L14R/L17R and L49R/L52R mutants did not. These results suggest that the K18-binding ability of the N-terminal Solo domain is critical for the ventral localization of Solo and its function in regulating mechanotransduction.

Original languageEnglish
Pages (from-to)390-402
Number of pages13
JournalGenes to Cells
Issue number5
Publication statusPublished - 2019 May


  • keratin
  • mechanotransduction
  • Rho-GEF
  • Solo
  • stress fiber
  • traction force
  • wrinkle assay


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